The present invention relates to an automatic thread cutting apparatus for sewing machines and particularly to a thread cutting apparatus that holds the yarn during yarn cutting after sewing operation has been completed for use in successive operations.
At present sewing technologies are quite mature. Adopted these technologies, textile industry is able to produce high quality clothes and garments at fast speed and lower costs to benefit people. Refer to FIGS. 1 and 2 for a conventional thread cutting apparatus used in sewing machines. It includes a first movable blade 61, a second movable blade 62, a first fixed blade 63 and a second fixed blade 64. The first movable blade 61 is for hooking a thread (not shown in the drawings). The first fixed blade 63 cuts off the thread. The second movable blade 62 is for hooking a bottom yarn, and the second fixed blade 64 cuts off the bottom yarn, then the bottom yarn (not shown in the drawings) is held. It needs two blades to cut off the thread and bottom yarn. The first and second movable blades 61 and 62, and the first and second fixed blades 63 and 64 are fastened to the bottom of a plate 65. When adjusting the angles of the movable blades 61 and 62, and fixed blades 63 and 64 is required, the plate 65 has to be removed, and the adjustment is performed on the plate 65. After the adjustment is completed, the plate 65 is reassembled on a sewing deck (not shown in the drawings) of the sewing machine again. If the plate 65 is not properly aligned and reassembled, the adjusted angles could be invalid. It causes a lot of inconveniences.
Therefore the primary object of the invention is to provide a thread cutting apparatus for sewing machines that employs a novel chain movement to drive the cutting mechanism of the sewing machines. The thread cutting apparatus according to the invention includes:
a thread cutter which consists of a cutting blade and fixed blades. The cutting blade and the fixed blades are mounted onto the top section of a sewing deck of the sewing machine. The fixed blades include an upper fixed blade and a lower fixed blade that are stacked over each other and spaced by a gap there between. The cutting blade may be swung through the upper and lower fixed blades to cut off the yarn. The cutting blade has a first cutting section to cut off the thread and a second cutting section to cut off the bottom yarn and clamp the remained portion of the bottom yarn. The first and second cutting sections have respectively a notch. The notch of the second cutting section is deeper than the notch of the first cutting section;
a linkage mechanism which consists of a direction switch section, a first crank lever, a second crank lever, and a first and a second linkage bar that are interconnected with each other by said order. The second linkage bar is connected to the cutting blade; and
a driver which drives the linkage mechanism moving in two directions to move the thread cutter to cut off the yarn. The driver is mounted on a bracing section, which is connected to a direction switch section of the linkage mechanism.
Another object of the invention is to provide a thread cutting apparatus that is easy to adjust and align. The thread cutter is directly mounted onto the sewing deck and covered by the plate. Adjustment of the cutting blade and fixed blades may be accomplished directly on the sewing deck to avoid errors.
The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.